Process and apparatus for treating paper-pulp.



G. C. HOWARD.

PROCESS AND APPARATUS FOR TREATING PAPER PULP.

APPLICATION FILED MAY 29. ms.

1 ,258,568. Patented Mar. 5, 1918.

WITNESSES: z 6 nvmvron K W 2/ 'f 27" ATTORNEY GUY c'. HOWARD, or TACOMA,WASHINGTON.

PROCESS AND APPARATUS FOR TREATING PAPER-PULP.

Specification of Letters Patent.

Patented Mar. 5, 1918.

Application filed May 29, 1916. Serial No. 100,460.

To all whom it may concern:

Be it known that I, GUY C. HOWARD, a

citizen of the United States, residin at Tacoma, in the county of Pierceand tate of "Washington, have invented certain new and usefulImprovements in Processes and Apparatus for Treating Paper-Pulp, ofwhich the following is a specification.

This invention relates to improvements in methods and apparatus fortreating the fibers of wood pulp for use in making paper, andparticularly to improvements in the operation known as heating the pulpwherein the fiber bundles are brushed, drawn out, and hydrated toimprove their quality in paper making;

The beating of pulp as commonly practised in paper mills is effected inthe socalled' Hollander or beating engine, and consists in causing thepulp to pass between a rapidly revolving roll and a stationary bed plateand wherein the fibers undergo a brushing out or drawing out, andhydration. Such brushing or drawing out action is mechanical, andconsists in a crushing and brushing of the fibers and, to a certainextent, flattening them.

Hydrating the pulp is a term signifying that the pulp has acquired asoft, greasy or slippery feeling and is supposedly due to the absorptionof water by the cellulose fibers.

Whether this absorption actually takes place to the extent supposed andwhether it is a mechanical or a semi-chemical absorption of water by thecellulose fibers, is not definitely known. The chemical nature ofcellulose would indicate more or less absorption of water by the fiberand result in its so-callcd hydration. At the same time, long continuedsoaking of the fiber in water does not effect the pronounced greasy feelto pulp that results from the beating treatment. The

, repeated passage of pulp through a centrifugal pump is reported asincreasing the hydration. The violent mechanical pounding impact andagitation produced on the pulp by the beater rolls is a factor tendingto increase the absorption of water by the cellulose fiber.

It is found in practical experiments with the present invention that theslippery, soft, greasy feeling to pulp beaten between the rolls of mysaid invent1on,is due more to the shape of the individual fibers afterbeating rather than to the actual hydration of the cellulose. Thenatural fiber from wood and other paper pulp materials is roughlycylindrical in cross section and many times its diameter in length. Itis hollow and with closed ends to the fibers. In dry wood, this voidinside the fiber is partially or wholly occupied by air. In wet wood, orin pulp, this space is more or less filled with water.

In the presently described treatment, these fibers are, to an extent,flattened out into what may be described as ribbon-shaped fibers ratherthan cylindrical, and the void inside the fiber eliminated by contact ofthe opposite fiber wall.

The flattening of pulp fibers in accordance with my invention andthereby giving them a somewhat ribbon shape instead of their naturalcylindrical shape in cross section, would produce the slippery, greasyfeeling which characterizes long-beaten pulp. 1

The hydration of the cellulose which gives it a rather more gelatinousstructure, is also a factor in giving certain propertles to beaten pulp,but by experiment it is found that the resulting sha e of the beatenfiber is the most important actor, and that to effeet a maximumflattening of the fibers wlth a minimum of actual hydration of thecellulose, improves the paper making quality of the pulp. In thisconnection, it 1s noted that graphite owes its lubricating propertiesprincipally to the thin flake-like shape of its individual particles.Tale is characterized by a cleavage into plates and has a greasyfeeling. Kaolin also occurs somewhat in scale-like crystals and isslippery to the touch, especially when: moist.

A fiber that is fiat and ribbon-like, is a better paper-making fiberthan when cylindrical in shape as it forms a stronger and better sheeton the paper machine wire due to both its carrying the free water longeron the wire and the fact that fibers of this shape will mat andinterlock more readily by the shake of the wire. it retains the fillerand mineral color better and gives a more uniform surface to the sheet.lit is also more compact both as regards thickness of the sheet for agiven weight and as regards flatness and compactness of surface which isa factor affecting the amount of sizing agent required. It makes a sheetthat is easier to dry because in pulp as ordinarily beaten and treatedin the Jordan engine, more or less free water is carried in the internalvoid space of the fibers and must be evaporated on the driers.Flattening the fibers would eliminate these voids and hence theirtendency to carry free water through to the driers.

The question is how this can best be accomplished when dealing withindividual fibers as minute and numerous as encountered in making asheet of paper. The common beater with revolving roll and stationary bedplate elfects this flattening action to some extent when the roll isdown hard and on such fibers as actually pass between the knife edge onthe roll and the bed plate.

The long treatment required to thoroughly beat pulp is evidently due tothe long time necessary to assure the major portion of the individualfibers actually having passed between the knife edge and the bed platewhen account is taken of the fact that some of the fibers are carriedpast the bed plate by the pockets in the roll.

Furthermore, if a flattening efiect is desired, the rubbing of the knifeedge pastthe stationarybed plate is not thought to be the propermechanical action to accomplish this although it probably does it to aslight extent. By experiment it is shown that the best flatteningefi'ect will be accomplished by a passing of fibers lengthwise betweentwo solid rolls. If the fibers were placed side by side and caused'topass lengthwise in a sin gle fiber thickness between two pressure rolls,the individual fibers would be fiattened out into ribbon shapes and theinternal void in each fiber would be eliminated by contact of oppositewalls of the fiber.

If quickly passed through the rolls, this flattening would probably beaccompanied by a bursting of the fiber wall at some point to allow theescape of water contained in the internal void.

The quality of softness and texture of fiber is regulated by the cookingprocess by which the pulp is made. l/Vith properly cooked stock, themost efiicient beater would be a machine which gives the maximumfiattening and bursting of the individual fibers with the minimum ofactual hydration of the cellulose. Such a beater may properly be calleda machine to ,super-calender the individual fibers before they are madeinto the sheet of paper.

intense The machine covered by this invention has for one of its objectsthe accomplishment of this efiect on the pulp. The ordinary beatergenerally works on pulp of relatively thick consistency and works to thebest advantage on such stock. The machine of my invention is designedfor either treating the stock in dilute consistency such as it existsbetween the paper machine screens and the lFourdrinier wire, or as itcomes from the pulp mill screens before being deckered.

A further object of the invention is to separate the pulp fibers passingthrough the rolls from a large percentage of the water with which it isconveyed to the point where the rolls effect their action, and therebyadapted for use as a decker or pulp thickener.

The machine made in accordance with my invention, however, will act uponthe stock in a thick consistency such as deckered stock similar to thatfurnished to the ordinary beater.

The invention consists in the method of treating paper stock, asheretofore outlined,

I roll of contact.

Tn the drawings, Figure 1 is a plan view of apparatus utilized with anembodiment of my invention. Fig. 2 is a transverse sectional view of thesame taken on line 22 of Fig. 1. Fig. 3 is a fragmentary detail view inhorizontal section showing the mannor of mounting the bearings of thecrushing rolls.

Referring to said views, the reference nu meral 1 indicates a vat ofsemi-circular form in cross-section having vertical end walls 2 and 3 inwhich cylindrical rolls 5 and 6 are rotatably mounted, and arrangedsymmetrically with respect to the interior configuration of the vat. Aninlet for-the admission of a mixture of pulp and water is Provided at 7upon one side of said vat and upon the opposite side an outlet 8arranged below the level of the inlet is pro vided with means to adjustthe-level of said outlet whereby the flow of pulp stock through the vatmay be more efliciently controlled.

Such means illustrated herewith consists of vertically arrangedguideways 10 formed or provided upon the side walls 2 and 3 of the vat,and one or more strips 11 of suitable widthsadapted to have theiropposite ends engage within said guideways and form a weir or gate overwhich the stock must flow and the relative heights of the inlet andoutlet adjusted.

12 indicates a launder or trough through which the pulp stock isconveyed to the vat and 13 a similar device to catch the overflow andconvey the same to its desired destination.

Said rolls 5 and 6 are each provided with axially disposed spindles 21which are mounted for rotation in journal-boxes 15 and 16, respectively,secured to the end walls 2 and J. The axes of said rolls are in paralleland'preferably arranged in horizontal relation, although theirarrangement in an inclined plane whereby the direction of the currentpassing between the rolls would be either substantially verticallyupward or upwardly inclined even to approaching. the horizontal, mayhave some merit and is contemplated in the scope of the invention.

The perimeters of the rolls are in close proximity, which point ofclosest proximity may be termed herein, for convenience, the pinch. Theclearance at the pinch is only such as to avoid as much as practicable,actual contact between the rolls although to get the desired flatteningeffect on fibers, it is essential that the rolls operate with aclearance between the rolls of less extent than the thickness of theindividual fibers.

The spindles 21 of the roll 5 are mounted in apertured bearing-blocks 17within the journal boxes 15 and a suitable hard rubber or othercushioning device 18 may be inserted therein to lessen the vibrationdeveloping from the relatively rapid rotation of the roll.

Thespindles 21 of the roll 6 are similarly mounted in bearing-blocks 20which are slidably secured in journal-boxes 16. A setscrew or equivalent23 threaded through the journal boxes 16 upon the side adjacent the roll5 and engaging the block 20 to limit the movement of the roll 6 towardthe companion roll 5.

A spring 25 engages each of the blocks 20 upon their opposite side,whose tension is regulated by means of set-screws 26.

It is essential that said rolls be driven at a relatively high speed,that is to say, about five hundred revolutions per minute in order todevelop a sufficient surface film friction with a relatively smoothsurfaced roll and to obtain the desired capacity and output.

Preferably the rolls are independently driven as by power belts 27 and28 engaging pulleys 30 and '31, respectively mounted upon the spindlesof the rolls 5 and 6.

For super-calendering or for the flattening effect upon the fibers, therolls should be driven at practically the same speed. A differentialsurface speed will effect a brushing or drawing out action upon thefibers at the line of contact, and when this is desired, the desiredrelative speeds may readily be given by reason of the independentdriving devices provided.

Where this differential motion is desirable is in treating relativelycoarse material in which the fibers exist in small bundles, as in groundwood screenings and, to a certain extent, in regular ground wood pulp,also in some cases in raw cooked sulfite. Such materials would generallybe treated in relatively thick consistency and with a minute abrasivesurface to the rolls.

One or both of said rolls are provided passage of a certain amount ofwater between the rolls to maintain proper consistency of pulp afterpassing and to assist in.

the approach of fiber to the pinch.

The grooves are relatively narrow and deep to give suitable crosssection area and still not materially reduce the lineof actual rollcontact.

F or a strictly flattening effect on the fibers, and where the surfacevelocity of the rolls is practically the same, a smooth polished surfaceon the roll will best serve the purpose. As above stated, where abrushing out of the fibers is desired, and where a differential surfacevelocity exists between rolls, a slightly rough or abrasive surface tothe rolls is advisable. It is not necessary or desirable that thissurface be rough to the extent of sand-stone or an emery wheel. What isdesired is a minutely rough surface commensurate with fiber dimensionsand for the purpose of simply preventing a slippage between the fiberand the surface of the rolls. For example, gray cast iron through thewearing away of its minute graphite particles under the action of pulpand water, should maintain under service sufficiently rough surface forthe purpose. The amount of this graphite constituent of the iron wouldnot be apparent on the pulp.

For smooth rolls, various materials suggest themselves as available,such as steel, bronze and hard rubber, and under some conditions the tworolls may be formed of different materials with desirable results; forexample, one of hard rubber and the other of steel or bronze.

Doctors 35 and 36 are slidably' mounted in guideways 37 in the end wallsof the vat and engage with the upper surface of the rolls 5 and 6respectively, whereby the course of the pulp travel through the vat andrelative to the rolls, may be controlled. The ends of the rolls make aclose running fit with the ends of the vvat. The arrangement anddisposition of the rolls in the vat, and the disposition of the doctors35 and 36 relative to the rolls, result in certain zones or areas beinformed within the vat that may be descri ed as follows Zone Awherein thepulp stock is received and flows through channel B owing to therelatively high hydraulic head usually maintained in this zone, and tothe filmfriction generated by the rapid revolution in the directionindicated by the arrow, of the roll 5.

The course of the pulp material and water carries it next into zone Cwhere the forces of therapidly revolving rolls 5 and 6 act upon the pulpand set up a variety of cross currents and eddies whlch effecta barrieragainst the further free progress of the pulp through the vat, thelarger part of the pulp material being drawn between the rolls andentering the zone D where, in the absence of the doctor 36, suchmaterial can flow directly out of the outlet 8.

A zone E is formed beyond the roll 6 which is principally white waterfrom which the pulp has been largely extracted. The rotation of the roll6 in the direction indicated by the arrow, resists the free movement ofthe water through the constricted passage F.

The rolls 5 and 6 being rapidly rotated in the directions indicated bythe respective arrows in Fig. 2, cause an upward movement or current ofwater and pulp through their points of closest roximity or pinch. Oneven a highly polishedroll running at the speed specified, there is avery thin friction zone at the surface which will carry pulp and waterup to the pinch. Even though this zone be very thin the surface velocityof the roll, together with its length, is ample to assure all the waterand pulp in even dilute stock being carried'to the pinch.

Water will be squeezed out of the pulp at the inch and the downwardvelocity energy of t is will maintain a distinct swirl of pulp and waterin the bottom of the vat. This swirl is eflected intending to bring allfibers into this thin friction zone on the surface of the rolls andthereby assist in their being caught at the pinch of the rolls. Thisswirl will maintain a natural bafiie to the pulp which will increase thetendency for it to be caught between the rolls before it can escapeunder the rolls 6 and thence out of the vat. The ooves32 in one or bothrolls will effect a s ight upward current, pulling the fibers into thepinch zone.

The speed at which the rolls can be run, together with the permissibleand practical length of such rolls, give a large capacity to a machineof this design even with a small clearance between rolls necessary toefle t a flattening of the individual fibers.

n consideration of the design and effect v narrates of this machine, itis noted that water is squeezed out of the pulp at the pinch of therolls, and consequently there is a tendency for pulp of thickconsistency to accumulate after passing the pinch, excepting as thisconsistency is modified by the water and some pulp which is allowed topass through the grooves on the face of one or both rolls; that is tosay, these high speed rolls eifect, to a certain extent, a separation ofwater from pulp. I

To make this action effective as a decker or pulp thickener, the contactdoctor 36, is placed on top of the roll 6 to prevent. the flow of thepulp through the discharge outlet 8 and provision is made to remove theaccumulated thickened pulp laterally at the ends of the roll above thepinch.

Such means consists in an opening 38 in one end wall of the vat, whichis provided with a sliding gate 39, said opening leading into a troughor launder 40. Some water, of course, will pass through the pinch of therolls and the groovesare designed in size to allow sufficient waterthrough to give proper consistency to the deckered stock.

A machine of this kind will have large capacity as a decker and besimple in operation and up-keep. It eliminates the necessity for anycylinder wires. A vat with a single pair of rolls should remove a largeproportion of the pulp.

It is obvious that a vat could be constructed with two or more pairs ofrolls if desired, although a vat with a single pair of rolls asillustrated would remove a sulficient percentage of ground Wood pulp toallow of on the grinders.

From chemical pulp, the white water,

from one set of rolls would be combined with other white waters andfinally cleaned ractical use of white water againf in either anotherroll vat or in suitable save-all.

What I claim as my invention, is-

1. The process of treating paper pulp, consisting in introducing pulpand water upon one side of a vat, causing said pulp and water to impingeupon the lower side of a pair of rapidly revolving rolls whereby thesurface friction of said rolls will draw the pulp between the rolls anddeliver the same thereabove, uniting the pulp and water in the vat atthe side opposite to said inlet, and discharging the pulp and water fromsaid vat at different points.

2. The process of treating paper pulp,

consisting in introducing pulp and water within a vat, causing saidmaterial to flow within the influence of a pair of rapidly revolvingrolls whereby the surface friction of said rolls will draw a portion ofsaid pulp and a reduced amount of water between the rolls to cause thesame to rise and float upon the remainder, and discharging said withdrawn pulp and water and the remainder of the water and pulp by separateoutlets.

3. In apparatus of the class described, ai vat, a pair of cylindricalcrushing rolls ro-.

tatably mounted in said vat and arranged to have their peripheralsurfaces spaced apart, means to maintain a continuous fiow of pul andwater within said vat at adjusted heights whereby said rolls aresubmerged and means to prevent the flow of the heavier pulp materialbeyond the roll.

4. In apparatus of the class described, a vat adapted to containwood-pulp and Water, a dpair of cooperating rolls rotatably mount e insaid vat, means to rotate said rolls in opposite directions wherebytheir surfaces at their closest proximity travel in upward directions,said rolls being spaced apart to admit of the passage of pulptherebetween and means to prevent the flow of the heavier pulp materialbeyond the rolls.

5. In ap aratus of the class described, a vat adapte to contain woodpulp and water, a pair of codperating rolls rotatably mounted in saidvat, means to rotate said rolls in opposite directions whereby theirsurfaces at their closest proximity travel in upward directions, saidrolls being spaced apart to admit of the passage of pulp therebetween, acircumferential groove formed upon the surface of one of said rolls forthe passage of pul and water and means to prevent the fiolviv o theheavier pulp material beyond the ro s.

6. In apparatus of the class described, a vat having an inlet at oneside thereof and an outlet at the opposite side of said vat, means toadjust the relative elevation of said inlet and outlet to control theflow of pulp and water through the vat, a pair of rolls rotatablymounted in the end walls of said vat, means to adjust the clearancebetween said rolls and means to prevent the flow of the heavier pulpmaterial beyond the rolls.

7. In apparatus of the class described, a vat having an inlet at oneside thereof and an outlet at'the opposite side of said vat, means toadjust the relative elevation of said inlet and outlet to control theflow of pulp and water through the vat, a pair of rolls rotatablymounted in the .end walls of said vat, means to adjust the clearancebetween said rolls, grooves formed upon the face of said rolls and meansto prevent the flow of the heavier pulp material beyond the rolls.

8 In apparatus of the class described, a vat having verticalsubstantially semi-circular'end walls and bottom and side walls ofsemi-circular configuration in cross-section, said vat having an inletupon one side and an outlet upon the other side, said outlet lbeingadjustable as to height, a pair of rolls having its bearings rotatablyjournaled in said end walls and arranged with their peripheral surfacesspaced from said bottom wall of said vat to afford restricted passagesfor the flow of liquid material toward said outlet and means to preventthe flow of the heavier pulp material beyond the rolls.

9. In apparatus of the class described, a vat adapted to contain wetpulp material, a. pair of cylindrical rolls rotatably mounted in saidvat,'one of said rolls having grooves formed in its periphery affordinga passage between said rolls for said pulp material, and means toprevent the flow of'the heavier pulp material beyond the rolls.

10. In apparatus of the class described, a vat, said vat having an inletupon one side and an outlet at its opposite side, said outlet being at alower elevation than said inlet, and a pair of rolls having theiraxially arranged spindles rotatably mounted in the end-walls of saidvat,-the axes of said rolls being in a substantially horizontal planeand at right angles to the flow of liquid material through said vat, anda doctor associated with the roll adjacent said inlet whereby the courseof said material toward said outlet is beneath said rolls.

11. In apparatus of the class described, a vat having an inlet and anoutlet for a mixture of pulp and water upon opposite sides of said vat,a pair of rolls rotatably mounted in said vat having their axes arrangedtransversely to the course of said mixture toward said outlet, an outletintermediate said inlet and said first named outlet whereby the materialpassed between said rolls may be discharged and means associated witheach roll to cause the mixture entering the vat to travel beneath thefirst roll and be substantially prevented from passing beyond the secondroll when fed upwardly therebetween.

12. In apparatus of the class described, a vat having an inlet at oneside thereof for a mixture of pulp and water, and an outlet at theopposite side of said vat for the dis charge of water, a pair of rollsrotatably mounted in the ends of said'vat having their axes arrangedtransversely to the course of said water from said inlet to the outlet,said rolls bein adapted when rotated to remove the pulp rom the water,an outlet in the end wall of said vat arranged above and intermediatesaid rolls whereby the pulp may be discharged and means associated witheach roll to cause the mixture enterin the vat to travel beneath thefirst roll and e substantially prevented from passing beyond the secondroll when fed upwardly therebetween- 13. In apparatus of the classdescribed, a vat having an inlet at one side thereof for a mixture ofulp and water, and an outlet at the oppos1te side of said vat for thedischarge of water, a pair of rolls rotatably mounted in the ends ofsaid vat having their Wall of said vat arranged above and intermediatesaid. rolls whereby the pulp may be discharged, and a doctor associated.with each of said rolls for directing the mixture entering the vat totravel beneath the first taaaaee roll, and be substantially preventedfrom 10 passing beyond the second roll when fed up wardly therebetweenoSigned at Tacoma, Washington, this 17th day of May, tale,

GWY U. HOWARD. Witnesses:

do A. finernn'r, C, R Boon.

